Increase in outer diameter of the rod cluster control assembly (RCCA) rodlets in a PWR plant was observed. Visual inspections of RCCA rodlets with large increases in outer diameter using a fiber scope and hot cell examinations of some RCCA rodlets lead to the following conclusions. 1 The increase in outer diameter was caused by the swelling of the absorber (Ag-In-Cd alloy). 2 At the RCCA rodlet tip, which was exposed to the largest amount of neutron fluence, an axial crack in the cladding tube was observed. 3 From the tensile test of cladding tube material, the uniform tensile strain was reduced to about 1.4% at 320°C due to neutron irradiation. In the slow strain-rate tensile test, intergranular cracking was observed. 4 From the above, it is considered that the axial cracking in the cladding tubes of PWR RCCA rodlets was caused mainly by a decrease in elongation due to neutron irradiation and an increase of hoop strain due to the swelling of the absorber.
|Number of pages||9|
|Journal||JSME International Journal, Series A: Mechanics and Material Engineering|
|Publication status||Published - 1995|
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